Electric fuse



Nov. 14, 1933. lr:q C, LA MAR 1,935,453

ELECTRIC FUSE Filed June 26. 1929 2 Z9 some Patented Nov. 14, 1933PATENT OFFIC.

Urrso STATES Fuse Company, New York,

N. Y., a'corporation of Delaware Appiicatien June 26, 1929. Serial No.373,725

11 Ciainis.

This invention relates to electric fuses, particularly to that type offuse known as an enclosed fuse andmore especially to such fuses of theknife blade type.

A principal object of this invention is the production of a fuse of thetype specified which consists of a minimum of parts necessarily detachedfor renewing the fusible element of such A further object is theproduction of a fuse of the type Yspecified in which at a maximum ofplaces a material is presented to the voiatiiized fuse metal which is ofsuch a nature that the volatilized fuse metal will practically notadhere thereto.

A further object of the invention is the production of a fuse of thetype specified in which the knife blades will be spaced a constantdistance apart by an insulating body so formed and positioned that itpresents a minimum of surfaces and obstruction to the free iiow of thevclatiiiaed metals and gases generated. Y

A further object of the invention is the production of a fuse of thetype specified which will provide a free but tortuous passage for theescape of volatilized fuse metal and gases.

Further objects and advantages will appear as the description of theparticular physical embodiment selected to illustrate the inventionprogresses and the novel features will be particularly pointed out inthe appended claims.

In describing the invention in detail and *he particular physicalembodiment selected to iii trate the invention reference is had to theaccompanying drawing wherein like characters of reference designate likeparts throughout the several views and in which:

Figure 1 is a longitudinal sectional view of physical embodiment of afuse selected to illustrate the invention; Fig. 2 is a longitudinalsectional view on the plane indicated by the line II-II of Fig. 1,viewed in the direction of the arrows at the ends of the line; 3 atransverse sectional View on the plane indi ted by the line III-III ofFig. 2, viewed in the direction of the arrows at the ends of the line;Fig. 4 is a transverse sectional View on the plane indi by the lineIV-IV of Fig. 2, viewed in the direction of the arrows at the ends ofthe line; 5 is a transverse-sectional view on the plane indicated by theline V-V of Fig. 2, viewed in the direction of the arrows at the ends ofthe line.

In order to illustrate my invention and the novel features thereof Ihave selected as a physical embodiment an enclosed type of fuseapproximating in general outline and construction well (Cl. 20G-131)known fuses of the prior art, altering the same only insofar as isnecessary to illustrate my invention and improvement.

The fuse employed to illustrate the invention is of the enclosed knifeblade type. It consists in general of an outer hollow enclosing shelland an inner fuse link and distance bar or fuse link unit includingprotruding knife blades, one at each end thereof together with suitableclosure members and means hereinafter known as screw caps for attachingthe parts rigidly together.

In Fig. 1 numeral l designates a hollow cylindrical body forming themain portion of the enclosing casing. The body 1 may be made of avariety of materials. I prefer hard vfibre, sometimes known as bonenbre. Each end of the main body 1 is preferably provided with a metallicferrule as 2. This ferrule is formed with internal crew threads 3engaging with cooperating eX- ternal threads upon the body 1 and itsdenite 75 position lengthwise of the body 1 is determined by thepresence of shoulder 4 abutting the end of the body 1. To render theunion between the main body l and the ferrule 2 more secure I prefer toemploy rivets 5 passing through the fer- 80 rules 2 and the main body l.The ferrule 2 is also provided with external screw threads 6 forcooperating with a cap 7 the particular function of which will behereinafter more fully explained.

Protruding from each end of the enclosing body formed of the main body 1and ferrules as 2 are knife blades as 8 and 9. In order to secure theknife blades 8 and 9 in spaced relation I employ the distance body 10.This distance body may be made of various appropriate materials but mypurposes I nd are best served by employing the same material that isused for the main body 1, that is, I preferably employ hard or bonenbre. In order to obtain a maximum of rigidity and best provide againstdistortion I prefer to employ the hard fibre 10 in the form ofapproximately a semi-circularshell. This approximate semi-circular formis best shown in Fig. 4. I also prefer to make the body 10 a somewhatless than a semi-circle so that the faces 11 and 12, as best shown inFig. 4 will not reach to or be adjacent the edges 13 and 14 of a knifeblade as 8.

In order to rigidly attach the body 10 to each of the knife blades 8 and9, I prefer to employ a semi-circular block 15, as best shown in Fig. 4.This semi-circular block 15 is interposed between kthe somewhatsemi-circular hard nbre body 10 and the tang end of a knife blade and110 then in order to secure the knife blade the block and the body 10rigidly together I pass the machine screws 16 and 17 through thesemi-circular body 10, the block 15 and into screw threaded oriiices 18.By this construction I obtain a construction which is easy to assembleand which also may be easily disassembled merely by the use of a screwdriver which inserted in the slot provided in all screws as 16 and 17will readily remove these screws and allow the parts to be separated sothat if necessary, by reason of darnage of excessive heat or otherwise,the hard fibre member 10 may be readily replaced. This block 15 may bemade of hard or bone fibre, or a metal such as aluminum which does notretain a deposit of volatilized fuse metal thereon.

In order to provide for the maximum of free flow of volatilized metaland gases generated by the blowing of a fuse link I remove a maximum ofthe material of body 10 between the end of the tang of the blade 8 andthe end of the tang of blade 9, as illustrated by 40 in Fig. 5, leavingin it an amount of material 10 found by experience to be suiiicient toact properly to space the tongues 8 and 9 and prevent undue distortionor misalignment thereof.

I provide a threaded hole as 19 in each of the tangs of the tongues 8and 9 which threaded hole is adapted to receive a machine screw, as 20,for the purpose of fastening one'end of the fusible link 21 conductivelyto a knife blade. In connection with the screw 20, I employ an aluminumwasher 22 which, as best shown in Fig. 4, is of such diameter that itmore than completely covers the slotted end 23 of the fuse link 21. Thepurpose of using an aluminum washer is to prevent an appreciable.deposit of volatiiized fuse metal at this point and the reason formaking the washer larger than the end of the fuse link is to protect asmuch as possible the end of the fuse link from a deposit of volatilizedmetal which would tend to solder the end of this link to the tang end ofthe knife blade. By this construction I am quite successful inpreventing lsoldering of the brass machine screw 20 to the washer, thewasher to the end of the fuse link and the fuse link to the tang of theknife blade. In order that there may be no impediment to the freepassage of the machine screw 20 into threaded hole 19 in the tang of theknife blade I provide a through hole or orifice 24 in the block 15, bestshown in Fig. 2, and in order to` be certain that nothing may lodge inthis hole 24, I carry the cut away portion of the `body V10 up to apoint as 25' and scarf block 15 as at 39, best shown in Fig. 2, whichmakes certain a clear passage through the tang of the blade, the block15 and the body 10, and makes an arrangement which requires a minimum oflongitudinal cutting of body l0.

In order to provide closures for the ends of the body 1 and at the sametime allow me to form the knife blades, the fusible link and thedistance body 10 as a unitary structure I make the closure arrangementfor the two ends slightly different.

The closure for the end of the body 1 adjacent the blade 8 includes analuminum washer 25 and a brass washer 26. The aluminum washer 25 has aslot therein through which the tang of the blade 8 may pass and thebrass washer 26 has a like slot. The brass washer 26, however, abutsshoulders 27 and 28 of the blade 8 so that both washers, after thescrews 16 and 17 are in place, are firmly held between the shoulders 27and 28 and the end of the body 10` and the end of the metallic block 15although I prefer to also solder washer 26 to the blade. They aluminumwasher 25 has several small projections as 29 formed in any appropriatemanner thereon. These projections 29 rest against the end of the ferrule2 and so slightly space aluminum washer 25 from the end of the ferrule2.

The closure adjacent the knife blade 9 includes a brass washer 30adapted to receive the tang of the blade. This Washer is by anyappropriate means rigidly attached to the blade 9. It may be solderedthereto. This washer 30 abuts the shoulders 31 and 32 of the knife blade9. In addition to the washer 30 there is a Washer 33 which has a slottherein through which the larger portion of the blade 9 may pass. Thiswasher is not permanently attached to the blade 9.

In addition to the washer 30 there is also an aluminum washer 34 in theform of a shallow cup positioned on the inner side of the washer 30 andextending up along the sides thereof. This washer or shallow aluminumcup 34 protects the brass washer 30 against the deposit of volatilizedfuse metal thereon. Although a rim is' preferred on the washer 34, it isto be understeed that this rim may be dispensed with.

In order to assemble the fuse the knife blades are connected by means ofthe body l0 as hereinbefore described and the fuse link 21. as put inplace together with washers 25 and 26 and 39 and 34 then with cap 7removed this assembly is passed endwise through the body 1 whereupon thecap 7 passed ove;` the knife blade 8 and screwed home bringingl theprojections 29 firmly against the ferrule 2 and the ange 36 against theoutside surfaces of the washer 26. Then the washer 33 is passed over theknife blade which may be done by reason of the presence of the slot inthe washer and afterwards cap 7 is placed over the washer and screwedhome upon the ferrule 2. When this assembly has been made there is aslight space between washer 33 and the end of ferrule 2 and also aslight space between the wall of ferrule 2 and the cup washer 34 and inaddition a slight space between the ends 37 of the caps 7 and theshculders 38 upon the ferrules 2. These spaces provide a free buttortuous path from the interior of the enclosing body 1 around throughthe screw threads 6 to the outside atmosphere for any volatilized gasesand metals generated within the casing.

By the construct-ion hereinbefovre described I have provided an enclosedknife blade fuse which may be disassembled by removing two caps as 7 andone washer as 33 and then withdrawn as a unitary device with the knifeblades 8 and 9 with their associated parts. When such blades 8 and 9have been withdrawn the fusible link 21 may be easily replaced byloosening two machine screws as 2O inserting a new fuse link andtightening the screws and the whole may then be reassembled in themanner hereinbefore described., without the use of any tools whatsover.Furthermore, the internal construction is such that washer 25 is spacedfrom the end of ferrule 2 by the projection 29 and washer 33 is spacedfrom the end of ferrule 2 by reason of the definite length given tomember l0 and a maximum of internal metallic parts which might becovered by a deposit of volatiliaed metal have been shielded by amaterial, preferably aluminum, which is resistant to deposit thereon ofa volatilized metal.

Csi

By the construction hereinbefore described it is undoubtedly true that agreater portion of the fusible metal ofthe link will be turned into agas than is customary ina fuse of this type but to provide for thiscontingency' I have cut away the greatest possible -portion of the bodyl0 so as to obviate any obstruction tothe free flow of the gases withinthe body 1 so that they may with the least resistance flow out at theends around the end of the ferrules 2 and through the screw threads 6 toissue at the small space provided therefor between 37 and 38.

Although I have particularly described only one particular physicalembodiment of my invention and explained the principle and operationthereof, nevertheless, I desire to have it understood that the formselected is merely illustrative but does not exhaust the possiblephysical embodiments of the idea of means underlying the invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is:

1. In a unitary fuse link device, in combination:

.a somewhat semi-circular, elongated, insulating body formed with alongitudinal cut away portion; a some-what semi-cylindrical blockpositioned on each end of the body; knife blade tangs, one bearing uponthe broad face of each semi- .cylindrical block; each of said tangsbeing provided with screw threaded orifices; machine lenclosing bodysurrounding the said parts and means for closing the open ends of saidbody and securing the said parts within the interior thereof.

.' 2. As a means for securing the tang end of 'a knife blade thecombination of a knife blade tang having a broad face; a semicylindricalblock having its flat face abutting the broad face of the tang, the saidblock being provided with an .orifice of major dimensions therethroughand 'with a plurality of orifices of minor dimensions therethrough; aninsulating spacing body of approximately semi-circular form; machinescrews passing through the said body and through the orifices of minordimensions in the block 'and screw threaded into the tang end of theknife blade whereby the orifices of maj or dimensions in block alignswith the screw threaded orifice in the tang, said body being provided.with a longitudinal cut away portion extending `to and including theorifice of major dimensions in the block.

3. In an electric fuse, in combination: a hollow enclosing body; afusible link therein; knife blades, one protruding from each end of theL'hollow body; screws for connecting the ends of the fuse links to theknife blades; threaded ferrules, one upon each end of the hollow body;screw caps, one engaging each of the ferrules; a

.closure washer at one end of the hollow body, vsaid -closure providedwith projections spacing it from the end of the ferrule; a flange on thescrew cap cooperating with the closure to hold the projections firmlyagainst the end of the ,ferrule whereby Volatilized metal and gasesblades, each provided with shoulders and each 'provided with tangs; adistance body intermediate the knife blades, said distance body beingformed of insulating material and arcuate in transverse section, thechord of the arc being spaced throughout to the same one side of theparallel surface of the tangs, and formed with a longitudinal cut awayportion of such extent as to leave a relatively slight amount ofmaterial at the ends thereof and means for connecting the distance bodyand the knife blades.

.5. As a fixed spacing means for the knife blades of an enclosedcartridge fuse of the knife blade type the combination of an insulatingbody arcuate in transverse cross-section extending from knife blade toknife blade and formed with a longitudinal cut away portion extending asubstantial distance under each tang and a semi-cylindrical block havingits curved surfaces tted into the concave surfaces of the arcuate bodyadjacent the end thereof and its flat face bearing against a broad faceof a tang together with machine screws passing through the arcuate bodyand the block into the knife blade tang.

6. As an end construction for a knife blade fuse of the enclosedcartridge type the combination of a knife blade formed with a tang andshoulders, of washers surrounding the tang and bearing against theshoulders and an insulating distance body bearing against the Washerspreventing endwise movement thereof together with a block interposedbetween the distance body and f the tang and means fastening thedistance body, the block and the tang securely together, the distancebody, tang and block formed with aligning orifices.

'7. In an enclosed cartridge fuse of the knife blade type thecombination of a knife blade having a tang and formed with a screwthreaded orice therein for the reception of a capscrew for holding theend of a fuse link, of semi-cylindrical blocks provided with an orificealigning with the screw threaded orifices in the tang, the curvedsurfaces thereof bearing against the distance body and means passingthrough the distance body and the block and the tang for securing theblock, the body and the tang together with the said distance bodyprovided with an orifice situated in alignment with an orifice in theblock whereby a through opening is provided below the cap screw in thetang.

8. In an enclosed electric fuse of the knife blade cartridge type havinga knife blade protruding from each end thereof, a distance body forspacing the knife blades a fixed distance apart, said body being formedarcuate in transverse cross-section and with a longitudinal cut awayportion for the greater portion of its length and means includingslotted washers and flanged screw caps for closing the ends adjacent theknife blades and for holding said knife blades in place.

9. In an electric fuse of the enclosed cartridge type having a knifeblade protruding from each end thereof, as a means for providing a freebut tortuous path for the flow of volatilized metal and gases from theinterior of the fuse to the atmosphere, the combination of a ferruleformed with an external screw thread positioned on the end of thecartridge, of a slotted substantially inflexible washer surounding aknife blade and a substantially similar size washer, formed of aluminum,provided with projections in the face thereof adapted to bear againstthe end of the ferrule positioned between the first mentioned washer andthe end of the ferrule and an inte-rnal threaded flange cap threadedupon the ferrule with the flange thereof bearing against the ide rstmentioned Washer whereby the' projections o n the second mentionedwasher are held firmly in contact with the end of the ferrule.

10. In an electric fuse, in combination: a hollow cylindrical body ofinsulating material; ex-

ternal threaded ferrules, one upon each end of the hollow body; knifeblades, one protruding from each end of the hollow body; a slottedWasher provided with projections in the `face thereof surrounding andheld in position on one o f the knife blades; a slotted Washersurrounding and held in position upon the other knife blade, said washerbeing of a diameter such that it may be passed through the hollow body;a removable slotted Washer surrounding the same knife blade as the lastmentioned washer; an insulating distance body attached at opposite ends,one to one of said knife blades and the other to the other of said knifeblades and of such length that the projections on the first mentionedwasher may bear tightly against the end of the ferrule adjacent theretoand the remQV- able washer on the other knife blade Will at the sametime bear tightly against the second mentioned washer, and internallythreaded flanged caps for cooperating with the threaded ierrules and thesaid washers to hold all parts firmly togelther, l

11. In an electric fuse, in combination; knife blades, each providedwith shoulders and each provided with tangs; a distance body intermefdiate the knife blades, said distance body being formed of insulatingmaterial and arcuate in transverse section, the chord of the arc beingspaced throughout to the same one side of the parallel surface of thetangs; and means for connecting the distance body and the knife blades.

FRANK C. LA MAR.

